Enhanced Thermostability, Thermo‐Optics, and Thermomechanical Properties of Barium Gallo‐Germanium Oxyfluoride Glasses and Glass‐Ceramics

Abstract

Serial substitutions of BaF 2 for BaO in BaO-Ga 2 O 3 -GeO 2 glasses were performed, and the effects of the substitutions on the glass properties were investigated. The glass transition temperature, density, refractive index, thermo-optics coefficient, and figure of merit for thermal shock decreased with the replacement of oxygen by fluorine. On the other hand, the glass-forming ability increased. Fluorine substitution removed the absorption band of hydroxyl near 2.9 lm. Raman scattering spectroscopy was used to characterize the fluorogermanate glasses. The crystallization process of the glass-ceramics under different heat-treatment conditions was also investigated using differential scanning calorimetry, X-ray diffraction, scanning electron microscopy, and atomic force microscopy. The thermal and mechanical properties were improved by controlling the crystal size of the near-and middle-infrared transparent glassceramics.

Transparent oxyfluoride glass ceramics

“…Glass ceramics based on fluorogermanate glasses belong to the same group of materials [224]. Introduction of BaF 2 to BaO-Ga 2 O 3 -GeO 2 glasses leads to the improvement of their optical transparency because of decreasing intensity of the absorption band intensity at about 3 microns (OH concentraton in the glass drops significantly), and transformation of the starting glass to glass ceramics (due to the appearance of BaGa 2 Ge 2 O 8 crystal phase) which essentially improves mechanical properties of the latter materials.…”

Optical Investigation of Ce3+‐Activated Borogermanate Glass Induced by Substitution of BaF2 for BaO

“…Both the excitation and emission intensity of Ce 3+ ions increases remarkably with the increasing substitution ratios, and the strongest emission intensity of the x = 20 glass is about 2.5 times higher than that of the x = 0.0 one. The enhanced emission intensity may be attributed to the combining factors: (i) the lower phonon‐energy of the designed glass with the further substitution of BaF 2 for BaO will be beneficial for the improvement of radiation probability, this have been extensively confirmed in oxyfluoride silicate and germanate glasses; (ii) the incorporation of fluorides, such as BaF 2 , into the designed germanate glass can considerably decrease the concentration of the ‐OH, which is usually considered to be a quenching center of activator; and (iii) the lower self‐absorption of Ce 3+ ions may be expected owing to the blue shift of the glass absorption edge with an increasing substitution ratio. Although the emission intensity of Ce 3+ ions ban be enhanced dramatically, the glass density decreases about 3.5% with the increasing substitution ratio, which has negative effect on the stopping power for the incident ionizing radiation.…”

“…To some extent, the partial substitution of BaO for Gd 2 O 3 barely influences the optical properties of borogermanate glass, which may guide to reduce the cost of raw materials. It is well‐known that the incorporation of alkaline‐earth fluorides, such as CaF 2 , SrF 2 and BaF 2 , into a silicate glass, will make a big difference in the thermal and optical properties to the formed oxyfluoride silicate glass or glass ceramic . Of course, this is also true for Er 3+ or Tm 3+ ‐doped barium gallo‐germanate glasses modified by the substitution of BaF 2 for BaO as infrared‐emitting materials .…”

Effect of Glass Refractive Index on Light Extraction Efficiency of Light‐Emitting Diodes

“…The refractive index is strongly related to the electronic polarizability of ions . The molar refractivity ( R m ) of an isotropic material, such as glass, is well described by the Lorentz–Lorenz equation:where is the reflection loss, M is the molecular weight, d is the density, M / d = V m is the molar volume, N is Avogadro's number, and α m is the molar polarizability. As shown in Eq.…”